AC balanced power schematic

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hello,

I'm planning on building a balanced AC power source. This will be a very simple one-in one-out affair, as I have a series-mode surge protector with all my equipment plugged into that, so I only need to plug the surge protector into the balanced power, and so, only one outlet.

My question: what sort of parts do I need for the unit, besides the center-tap transformer? I don't believe I need any sort of surge-protection, as the load won't permit any excessive current-draw. I'm assuming a filter would be necessary (EMI, RFI???)...

Any schematics or ideas greatly appreciated...

thanks,

-tal
 
balanced AC power

hello,

I'm trying to achieve balanced AC power - 60 volts to each direction from ground, a clean 120 between them. That's all. the only difference, is that I'll be using a surge protector downstream, with all my equipment plugged into it, so I only need one outlet. I'm just wondering what to have in the box besides the actual center-tap transformer. If it's as simple as an Auricap across the input of the transformer, then that's dandy. I just want confirmation of that.

thanks,

-tal
 
You will want to ensure the the transformer you use is Bifilar wound to ensure the two secondaries are 180 out of phase. A centre tap is not what you are looking for. You will need Dual secondaries, centre tap transformers are often just one coil, wound in one direction with a voltage tap in the centre.

One connecting the two secondaries there are several connection themes. The most dangerous uses the ground as a common return for the two balanced 60VAC feeds, this also happens to be the best for eliminating noise, in theory as the two AC lines are truly balanced. The accepted mode under electrical code is two use one side of the output as Hot and the other side as neutral. This causes no current to flow to the ground throw the centre connected coils. The difference is in which side of the secondaries you connect together, as they can be connected in and out of phase. Both connections provide a balanced output, though one can be deadly and the other quite safe. There are some white papers and a special deal on the correct transformer to use at www.plitron.com


Regards

Anthony
 
schematic!

Coulomb,

Do you have a schematic for what you're describing? I can somewhat figure out what you're saying, but a schematic would eliminate all doubt...

I'm actually not sure what the transformer is... I haven't seen it yet. It's a 40 amp continuous unit from the 70's from my father... if it isn't suitable, I'll just get one of the Equi-Tech units from the following site:

http://www.equitech.com/products/seconds/seconds.html

It's $400 but it's a really nice piece, literally ideal for what's needed...

thanks again,

-tal
 
Prune said:
Coulomb (ref: post 5), what's the difference between the first configuration you are proposing and the others (the others being the in-phase and out-of-phase)? Your post is not clear; please elaborate.


If you wire the Secondaries to a load in a truly out of phase configuration the load will see no potential difference as they would cancel each other. If you were to bring the centre tap to ground in this configuration you would have 60 VAC across ground and each side of the secondaries. If you feed a toroid with dual 120vac primaries such as a 120/240 model with dual 60 VAC out of phase, each coil in the primary of the powered transformer would perfectly balanced and you would get a real nice 120 VAC out instead of 240 VAC out. It is cumbersome and vitally important you keep chassis ground isolated from power out ground. It is expensive because you have a dedicated balancing transformer for every power transformer, but it is decandently effectivwe at completely isolating the mains from your power transformer. This is also very dangerous and should not be attempted by anything short of a licensed electrician.

Regards

Anthony
 
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Joined 2003
I think I see now. So in this configuration, you need four conductors, since earth ground is separate from the inter-transformer center tap return one. In the standard configuration, you are just making the center tap be referenced to ground (instead of neutral).

Now, it's not clear to me what advantage there is from the second configuration (as opposed to just using a standard isolation transformer). How does having ground between hot and neutral help?
 
Pardon my ignorance, but I'm a bit confused by this issue. Let's say, I have a a power amplifier that has a true ground for a neutral on the binding posts. (two Counterpoint SA-220 amps and a NPS-200 amp, and two Modded Belles 450 amps) All true ground, on the (-) terminal on the power amp.

Now, When I connect the balanced transformer, the deal is on the 120AC INPUT side of the transformer, I should be sure that there is NO ground connectivity, other than the chassis I choose to put the transformer in? Ie, the neutral on the input side of the transformer (the 120AC North American power system) should NOT be connected to ground potential? That makes sense to me. Ie, no ground connectivity on the input side of the balancing transformer. I can see where the disaster lies in wait....Kaboom! But the output side of the balancing transformer should have it's center tap connected to 120AC ground AND transformer 'chassis' ground.

If I should choose to put the balancing transformer in a 'chassis' (no chassis), otherwise, the Balancing transformer's Input ground (the 120 AC ground) should be connected to the Balancing transformer's OUTPUT center tap. This becomes the ground for the balanced AC output of this little balancing act. (this, considering that there is to be NO 120VAC ground AT ALL on the balancing transformer's 120 VAC INPUT side, no matter the design, ie, 120/240 wiring on the input side)

What about ground shields on the input side of the balancing transformer?

I'm looking at buying a few of the 120/240AC dual wound (but have to check with plitron for bifilar!) dual out transformers they have for sale, in order to get some balanced AC in the house.

Now, do I have this right? It seems I do..... I like to be absolutely sure when messing with high power 120AC systems, however basic the whole thing may seem.
 
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